This is described in Annex IV, V and VI [1]. You must do a conformity assessment and provide a declaration of conformity. For non-critical software you can do the assessment yourself see the first five points in Annex VI.
The only thing that maybe requires a bit of effort is that you must write some technical documentation including a cybersecurity risk assessment during the assessment if you have not already done so. For critical software the process is of course a bit more involved because it requires certification by a "notified body".
[1] https://eur-lex.europa.eu/resource.html?uri=cellar:864f472b-...